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Makes 🢒 GMC_Truck 🢒 1999 🢒 Envoy - 4WD 🢒 DTC 🢒 DTC B0180 Output Air Temp Sensor 2 Circuit Low

DTC B0180 Output Air Temp Sensor 2 Circuit Low Lower


Object Number: 394206 Size: MF
HVAC Components
Cell 68: ECC Module and Temperature Sensors
Handling ESD Sensitive Parts Notice
Cell 68: ECC Module and Temperature Sensors

Circuit Description

The lower discharge air temperature sensor is a thermistor used in order to control the signal voltage in the electronic climate control (ECC) module. The ECC module supplies a reference voltage (about 5 volts) on CKT 405 to the sensor. When the lower duct air temperature is cold, the thermistor resistance is high. Therefore, the ECC module will receive a high voltage input. If the lower duct air temperature is hot, the thermistor resistance is low. Therefore, the ECC module will receive a low signal voltage input. The lower discharge air temperature sensor is used in order to enhance the temperature control. Refer to Sensor Resistance Table .

Conditions for Setting the DTC

When the ignition is ON, the ECC module will detect this fault any time that CKT 405 is at or near 5 volts or higher.

Action Taken When the DTC Sets

The ECC module will use a default value of 10 A/D counts until the fault is cleared.

Conditions for Clearing the MIL/DTC

This fault will clear as soon as DTC B0180 disappears or is repaired. The system will then return to normal operation. History DTCs may only be cleared by removing and restoring B+ or by using the scan tool.

Diagnostic Aids
    • The ECC module may set class 2 lost communication DTCs when the body control module (BCM) or the vehicle control module (VCM) is being reprogrammed. After reprogramming, inspect for DTCs in the ECC module. Clear any history U DTCs, then resume diagnostics.
    • Visually inspect the sensor connector and harness for corrosion and damage. The resistance value of the sensor must be 334-100,865 ohms. Refer to Sensor Resistance Table . If resistance is not within specifications, replace the sensor.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step measures the resistance of the lower discharge air temperature sensor.

    2.

  2. This step inspects for a short to ground in CKT 405.

    3.

  3. This step inspects for intermittents and tests for a malfunctioning ECC module.

    4.

  4. This step repairs the short to ground in CKT 405.

    5.

  5. This step replaces a defective lower discharge air temperature sensor.

    6.

  6. This step replaces a defective ECC module.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the lower discharge air temperature sensor.
  3. Measure the resistance between sensor terminal A and terminal B.

Is the resistance less than the specified value?

5 ohms

Go to Step 3

Go to Step 6

3

  1. Disconnect the ECC module.
  2. Inspect for a short to ground in CKT 405 (LT GRN) at terminal C3 of the ECC module harness connector.

Is continuity present?

--

Go to Step 5

Go to Step 4

4

  1. Reconnect the lower discharge air temperature sensor.
  2. Reconnect the ECC module.
  3. Turn the ignition switch to the ON position.
  4. Clear any ECC module DTCs.

Does the DTC clear?

--

Go to Step 7

Go to Intermittents and Poor Connections Diagnosis in Wiring Systems

5

Repair the short to ground in CKT 405 (LT GRN).

Is the repair complete?

--

Go to Diagnostic System Check

--

6

Replace lower discharge air temperature sensor. Refer to Floor Air Outlet Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check

--

7

Replace the ECC module. Refer to Control Assembly Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check

--